The present invention generally relates to display mode selection methods and display unit controllers, and more particularly to a display mode selection method for selecting a display mode with respect to an input display signal from a plurality of display modes, and to a display unit controller which employs such a display mode selection method.
The display mode of the display unit may be fixed if the horizontal scanning frequency, the vertical scanning frequency, the polarities of the horizontal and vertical scanning frequencies, the resolution and the like of the input display signal are constant. But recently, there are demands to display the input display signal in various display modes, and it has become possible for one display unit to make the display in a plurality of display modes.
The display unit which is capable of making the display in a plurality of display modes is provided with a table which stores the horizontal scanning frequency, the vertical scanning frequency, the polarities of the horizontal and vertical scanning frequencies, the resolution and the like for each of the displayable display modes. FIG. 1 is a diagram showing an example of such a table. As shown in FIG. 1, an identification (iD) number is assigned to each display mode, and the table stores the horizontal scanning frequency fH and its polarity, the vertical scanning frequency fV and its polarity, the resolution and other display screen controlling parameters with respect to each iD number. The other display screen controlling parameters with respect to the input display signal which includes red (R), green (G) and blue (B) signals and horizontal and vertical synchronizing signals are selected by making a reference to the table based on the horizontal scanning frequency, the vertical scanning frequency and the polarities of the horizontal and vertical scanning frequencies of the input display signal. An iD number 16 is provided with respect to an unknown display mode.
As may be seen from FIG. 1, a plurality of display modes exist even for the same horizontal scanning frequency, and a plurality of display modes exist even for the same vertical scanning frequency. For this reason, a conventional display mode selection method selects from the table a display mode with respect to the input display signal, by successively comparing the parameters such as the horizontal and vertical scanning frequencies of the input display signal and the polarities of the horizontal and vertical scanning frequencies and the parameters which are store din the table with respect to each of the iD numbers.
However, according to the conventional display mode selection method, there was a problem in that a processing time required to select the display mode is long because the display mode with respect to the input display signal is selected from the table by successively comparing the parameters of the input display signal and the parameters which are stored in the table with respect to each of the iD numbers.